The newspaper printing system disclosed and claimed in this application relates to improvements in printing presses of the type disclosed in my Canadian Pat. No. 938,832 issued Dec. 25, 1973 and relates specifically to simplifying existing lithographic printing processes for publishing newspapers, books and the like on coarse, rough, absorbent pulp paper. Newsprint type paper is very coarse having a large amount of loose fibers on the surface of the paper.
Heretofore, attempts to achieve quality printing on both sides of a web have utilized opposed offset blankets mounted on cylinders. The blankets accumulate ink and tend to collect loose fibers and lint and thereby has been limited in use on newsprint paper because of the accumulation of ink and lint on the blankets and in the inking train necessitating cleaning of the blankets on the blanket cylinders.
Heretofore, presses which have attempted to print directly on both sides of newsprint, as disclosed in Canadian Pat. No. 938,832 and U.S. Pat. No. 926,102 have utilized conventional inkers.
Conventional inkers for lithographic printing plates used for printing on newsprint which have achieved "commercial" acceptance generally comprise from two to four form rollers which are positioned in rolling engagement with the printing plate. Each of the form rollers is usually in rolling engagement with one or more vibrator rollers to which ink is applied by several rollers in a train of rollers of varying diameters arranged in pyramid fashion. Ink is delivered to the train of rollers over a ductor roller which oscillates into and out of engagement with a film of ink formed by a doctor blade urged into engagement with the hard surface on an ink fountain roller by numerous ink keys.
The ink film formed on the ink fountain roller has been too thick and too irregular for application directly to a printing plate for quality printing. These inkers which include a multiplicity of rollers are intended to reduce the thickness of the ink film and to deliver a film of uniform thickness to the printing plate. However, since the ink film on each of the rollers is not totally replenished on each revolution of the form roller; image ghosting and ink accumulation and starvation is not completely eliminated. Thus, streaks and uneven ink distributions are produced on the product due to the ghosting and ink accumulation and/or starvation.
The multiple form roller, conventional inkers require complex drive trains and are relatively expensive to purchase initially and to maintain thereafter.
Other types of inkers which have attempted to meter ink from a transfer roller to a form roller have utilized a doctor blade to remove all of the film of feedback ink from the form roller prior to replenishing the ink film. Since most form rollers are resilient, the contact of the doctor blade to the form roller surface may score the form roller and wear out the blade and roller causing an uneven film of ink.
The invention described herein addresses the problem of direct printing with opposed plates engaging opposite side of a web of newsprint simultaneously without the use of offset blankets by utilizing inkers which control accumulation of ink and dampening fluid to control accumulation of lint, while eliminating the conventional train of rollers in the inking system, eliminating the necessity for the consumption of excessive power and further reducing and eliminating numerous adjustments and areas of ghosting and ink accumulation and starvation which produce undesirable variations on the product being printed.
Devices of the type disclosed in U.S. Pat. No. 3,926,114 were devised to remove all the unused portion of ink and dampening fluid from the form roller prior to forming a new film of ink by metering the ink between the form roller and a transfer roller. There may be considerable wear on the ink removal blade and the roller in this type of device. Also, it is extremely difficult to form an ink film which is sufficiently thin by using a doctor blade when metering newsprint ink.
Inking devices of the type disclosed in U.S. Pat. No. 2,240,762 employ rollers having cavities formed in the surface to meter ink onto a form roller for application to a printing plate.
An improved inker and dampener structure is described herein for applying a controlled film of ink to both sides of newsprint by direct lithography as the web of newsprint moves directly between two opposing lithographic plates. The inker and dampener cooperate together on a single form roller to eliminate excessive accumulation of ink and dampening fluid to eliminate accumulation of lint and fiber on the plate or inking and dampening system.
A pair of opposing plates simulatenously engage opposite sides of a newsprint web to print thereon. Substantially identical inkers and dampeners apply ink and dampening fluid to each opposing plate as hereinafter described.